FIG. 1 illustrates a wind turbine 1, comprising a wind turbine tower 2 on which a wind turbine nacelle 3 is mounted. At least one rotor blade 5 is attached to a hub to form the rotor 4. Each blade can rotate about its own longitudinal axis. This is called blade pitching. The hub 6 is connected to the nacelle 3 through a shaft (not shown), preferably being a low speed shaft, extending from the nacelle front. The wind turbine illustrated in FIG. 1 may be a small model intended for domestic or light utility usage, or may be a large model, such as those that are suitable for use in large scale electricity generation on a wind farm. In the latter case, the diameter of the rotor 4 may be as large as 150 meters or more.
The rotor blades of wind turbines are designed to extract power from the wind by virtue of their aerodynamic shape, and subsequent wind induced rotation. For horizontal axis wind turbines, the rotation of the rotor about its axis turns a drive shaft connected in turn to a generator which produces electricity. A low speed drive shaft may be used, coupled to a high speed shaft, or alternatively a direct drive shaft may be used. For horizontal axis wind turbines to operate efficiently and extract the maximum power from the wind, the wind turbine nacelle is rotated to make the rotor face the wind to the greatest extent possible, such that the rotational axis of the rotor is aligned with the wind direction.
Wind turbines, and in particular larger wind turbines, will have a system for rotating the nacelle such that the rotor is oriented to face the wind. These systems are commonly known as yaw systems, or azimuth drives, and allow a wind turbine to continue to extract maximum energy from oncoming winds, despite changes in wind direction. The yaw system is usually located between the wind turbine tower and the nacelle and typically comprises a bearing that is fully rotatable around an axis co-linear with the tower, and one or more electric or hydraulic drives for rotating the bearing relative to the tower. In this way, the nacelle, mounted on the bearing, can be turned through 360 degrees in the horizontal plane.
It can be seen that operating parameters such as the yaw and blade pitch can be adjusted in view of prevailing weather conditions such as wind direction and speed. This may include adjustments to increase or decrease power production, or to reduce strain on the turbine components. This may also include shutting down the turbine, for example by feathering the blades, in response to large gusts or other extreme weather conditions.
Due to the size of modern wind turbines they are susceptible to collision with moving objects such as aircraft. A collision between an aircraft and a wind turbine could clearly result in loss of life and considerable damage to both the aircraft and the wind turbine.
There is a need for a wind turbine featuring a detection system for detecting moving objects such as aircraft, allowing action to be taken in response to the detection. There is also a conflicting need for a wind turbine featuring a detection system to detect weather properties so that appropriate action can be taken.